Construction of Listeria monocytogenes Mutants with In‐Frame Deletions in the Phosphotransferase Transport System (PTS) and Analysis of Their Growth under Stress Conditions

Listeria monocytogenes is a foodborne pathogen that is difficult to eliminate due to its ability to survive under different stress conditions such as low pH and high salt. To better control this pathogen in food, it is important to understand its survival mechanisms under these stress conditions. LMOf2365_0442, 0443, and 0444 encode for phosphotransferase transport system (PTS) permease (fructose‐specific IIABC components) that is responsible for sugar transport. LMOf2365_0445 encodes for glycosyl hydrolase. These genes were induced by high pressure and inhibited under salt treatments; therefore, we hypothesized that genes encoding these PTS proteins may be involved in general stress responses. To study the function of these genes, deletion mutants of the PTS genes (LMOf2365_0442, LMOf2365_0443, and LMOf2365_0444) and the downstream gene LMOf2365_0445 were created in L. monocytogenes strain F2365. These deletion mutants were tested under different stress conditions. The growth of ?LMOf2365_0445 was increased under nisin (125 μg/mL) treatments compared to the wild‐type (P < 0.01). The growth of ?LMOf2365_0442 in salt (brain–heart infusion medium with 5% NaCl) was significantly increased (P < 0.01), and ?LMOf2365_0442 showed increased growth under acidic conditions (pH 5.0) compared to the wild‐type (P < 0.01). The results from phenotypic arrays demonstrated that some of these mutants showed slightly slower growth under different carbon sources and basic conditions. The results indicate that deletion mutants ?LMOf2365_0442 and ?LMOf2365_0445 were more resistant to multiple stress conditions compared to the wild‐type, suggesting that they may contribute to the general stress response in L. monocytogenes. An understanding of the growth of these mutants under multiple stress conditions may assist in the development of intervention strategies to control L. monocytogenes in food.     

A numerical model for delamination growth simulation in non-crimp fabric composites

In this paper, a novel finite-element tool, for the simulation of delamination growth in non-crimp fabric (NCF) composite materials, is presented. The proposed finite-element tool is based on the stiffness averaging method (SAM), on the modified virtual crack closure technique (MVCCT) and on the penalty method (PM); all these methods have been implemented in the research oriented B2000 finite-element code. The stiffness averaging method allows taking into account the effects of the processing variables, which characterize the representative volume element (RVE) of the non-crimp fiber composites (NCF) on their mechanical performances; while the modified virtual crack closure technique is used to determine the strain energy release rate (SERR) for the delamination growth. Already available experimental data on Mode I fracture toughness, obtained by using double cantilever beam (DCB) tests have been employed for validation purpose of numerical procedure. The modeling of DCB tests, considering different geometrical cases, has been performed by means of non-linear analyses. Excellent results in terms of deformed shapes and load–displacement curve, compared with experimental data, are reported to support the validity and the accuracy of the presented computational procedure. Moreover, the ability of the developed tool to take account for the NCF performances variability with processing parameters along with the delamination growth has been assessed and critically discussed.     

Communication in Chemical Emergencies

In the case of chemical emergencies, public information must be given high priority in both planning and management. The public information requirement concerning major accident hazards has been incorporated into Community legislation since 1982 as a relevant component of the control of major accident hazards. During an emergency, communication is to be recognised as the most critical factor that determines the success of the response. However, during an emergency, while the dynamics of events and processes may be partially obscure, people must still be warned of impending danger. The management of ‘in the event’ information is quite diverse from that of ‘prior’ information.     

Coexistence of Negative and Positive Photoconductivity in Few-Layer PtSe2 Field-Effect Transistors

Platinum diselenide (PtSe₂) field-effect transistors with ultrathin channel regions exhibit p-type electrical conductivity that is sensitive to temperature and environmental pressure. Exposure to a supercontinuum white light source reveals that positive and negative photoconductivity coexists in the same device. The dominance of one type of photoconductivity over the other is controlled by environmental pressure. Indeed, positive photoconductivity observed in high vacuum converts to negative photoconductivity when the pressure is raised. Density functional theory calculations confirm that physisorbed oxygen molecules on the PtSe₂ surface act as acceptors. The desorption of oxygen molecules from the surface, caused by light irradiation, leads to decreased carrier concentration in the channel conductivity. The understanding of the charge transfer occurring between the physisorbed oxygen molecules and the PtSe₂ film provides an effective route for modulating the density of carriers and the optical properties of the material.     

K maximum probability attack paths generation algorithm for target nodes in networked systems

International Journal of Information Security - As known, security system administrators need to be aware of the security risks and abnormal behaviors in a network system. Given the exploitation...     

Heparin conjugated silica nanoparticle synthesis

We report on a facile method towards a synthesis of novel hybrid heparin silica nanoparticles involving a modification of the Stober method. Tetrapropyl orthosilicate (TPOS) was used instead of the traditional TEOS or TMOS; by this way we could overcome the solubility problems of heparin in ethanol and exploit the good solubility of heparin in proper isopropanol–water mixtures. Aminopropyl triethoxysilane (APTS) was also used to have a good link of heparin to silica particles. SEM, DLS, FTIR and NMR proved that we did find conditions in which heparin conjugated silica particles were produced.Thermogravimetry allowed to evaluate the heparin/silica weight ratio to be 0.61. The efficiency of heparin binding to the particles was appreciated to be 35 wt.%.     

Circulation and horizontal fluxes in the northern Adriatic Sea in the period June 1999-July 2002. Part II: nutrients transport

Nutrient concentrations (orthophosphate, orthosilicate and dissolved inorganic nitrogen-DIN) were measured on three transects in the northern Adriatic approximately monthly in the period June 1999-July 2002. The net nutrient transports across the three transects were estimated from these concentration values and calculated water fluxes [Grilli F, Paschini E, Russo A, Precali R, Supi? N. Circulation and horizontal fluxes in the Northern Adriatic Sea in the period June 1999_July 2002. Part I: geostrophic circulation and current measurement. Sci Total Environ 2005-this issue], with the aim to verify their possible role in the mucilage phenomenon. The nutrient transports in the northern Adriatic were very variable, seasonally and from year to year, both in intensity and direction. Some differences were noticed also among the nutrient species. At the northernmost transect Po Delta-Rovinj minimal values and variable directions were recorded, probably due to the prevailing of eastward transversal transports, observed already in late winter, and generally dominant in spring and summer. Northward transport was often measured at the central transect Cesenatico-Cape Kamenjak, particularly in spring 2000 and 2002, and summer 2001, as well as for only DIN in summer 1999. In contrast, southward directions prevailed at the southernmost transect Senigallia-Susak Island. In October significant southward transports occurred at all transects and for all nutrients, particularly strong in 2000, when exceptionally high Po River discharges occurred, and the Western Adriatic Current (WAC) was well developed. However, the nutrient transports in the upper water column were low or northwards at both transect Cesenatico-Cape Kamenjak and Senigallia-Susak Island in June and July 2000, 2001, and 2002, when the mucilage phenomenon developed, but were opposite in 1999, a year without events. The results suggest that high variations of nutrient fluxes and their ratios, in conditions of reduced water dynamics, are essential for the development of the phenomenon, rather than the absolute amounts of the nutrient inputs.     

Circulation and horizontal fluxes in the northern Adriatic Sea in the period June 1999-July 2002. Part I: geostrophic circulation and current measurement

The dramatic increase in the occurrence of massive mucilage events in the northern Adriatic (NA) since their recent conspicuous reappearance in the late 1980s prompted a study of circulation and horizontal fluxes. Three transects with equidistant stations (10 km) were thus monitored monthly between June 1999 and July 2002. The geostrophic method was used to compute currents across the three transects from the CTD data, and dynamic heights provided a picture of the horizontal surface circulation. Currentmeter data records were used to adjust the reference surface and to validate the results for the southernmost and deeper (up to 70 m) transect (Senigallia-Susak Island). Geostrophic currents allowed estimation of monthly water fluxes across the transect. Different circulation regimes in the NA were observed, which may have affected mucilage events. When mucilage was absent (1999) or reduced (2001) in the western sector, the Western Adriatic Current (WAC, carrying water out of the NA) was found to be active, whilst the WAC was very weak or reversed when massive mucilage events occurred (2000 and 2002). Opposite behaviour has been observed for the Istrian Coastal Counter-Current (ICCC, retaining freshwater water in the NA) which was more intense during or after massive mucilage events and did not appear when mucilage was absent. Both WAC weakening and ICCC strengthening indicate a longer residence time of riverine waters in the NA, which favours mucilage development. Conclusively, WAC and ICCC result as key elements in controlling massive mucilage phenomena in the NA.     

Fate of eprinomectin in goat milk and cheeses with different ripening times following pour-on administration

The distribution of eprinomectin in goat milk and cheeses (cacioricotta, caciotta, caprilisco) with different ripening times following a pour-on administration at a single dose rate (500 microg/kg of body weight) and a double dose rate (1,000 microg/kg of body weight) to goats with naturally occurring infections of gastrointestinal nematodes was studied. Milk residues of eprinomectin reached a maximum of 0.55+/-0.18 microg/kg and 1.70+/-0.31 microg/kg at the single and double doses, respectively. The drug concentrations decreased progressively until the fifth day after treatment, when they were less than the detection limit at both dose rates. The eprinomectin levels measured in all cheese types (both treatments) were higher than those recovered in milk at all the sampling times. In caciotta cheeses, the eprinomectin residues levels were constantly higher than other cheeses. With the exception of cheeses made with milk the first day after treatment, eprinomectin concentrations were nearly constant up to the fourth day then decreased by the fifth and sixth days after treatment. In all cases, at both the single and double dosages, the maximum level of eprinomectin residues in goat milk and cheeses remained below the maximum residual level of 20 microg/liter permitted for lactating cattle.     

A secure file sharing service for distributed computing environments

Distributed cryptographic file systems enable file sharing among their users and need the adoption of a key management scheme for the distribution of the cryptographic keys to authorized users according to their specific degree of trust. In this paper we describe the architecture of a basic secure file sharing facility relying on a multi-party threshold-based key-sharing scheme that can be overlaid on top of the existing stackable networked file systems, and discuss its application to the implementation of distributed cryptographic file systems. It provides flexible access control policies supporting multiple combination of roles and trust profiles. A proof of concept prototype implementation within the Linux operating system framework demonstrated its effectiveness in terms of performance and security robustness.